Spinal implant insertion instrument for spinal interbody prostheses

ABSTRACT

A spinal implant insertion instrument for intervertebral implant surgery formed from a hollow first element of various external diameters, including a channel to accommodate and incorporate a vertebral pedicle, and a second element joined by a hinge to the first element, allowing reduction of the external diameter of the leading edge of the spinal implant insertion element sufficient to allow the passage of the spinal implant insertion instrument into the intervertebral disc space in a safe fashion, as the first maneuver, to be followed by activation of the second element upon the first, restoring the internal diameter of the spinal implant insertion instrument to a sufficient radius to allow successive passage of cutting, reaming, tapping instruments, and subsequent implantation of a spinal interbody implant device. The design of this instrument reduces traction upon sensitive neural elements, allows controlled removal of the medial portion of the vertebral pedicle, distracts the intervertebral disc space, and allows safe passage of reaming, tapping, and spinal implant insertion devices through the expanded bore of the spinal implant insertion instrument.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is a continuation of application Ser. No. 09/570,648,filed May 15, 2000; now U.S. Pat. No. 6,520,967, which claims thebenefit of U.S. Provisional Application No. 60/160,711, filed Oct. 20,1999.

FIELD OF THE INVENTION

The invention relates generally to a spinal implant instrument for usein intervertebral spinal fusions, and more specifically, to an improvedmethod of protection for neural elements during intervertebral discspace distraction, disc space reaming and tapping, and placement ofintervertebral disc space bone grafts and prosthetic devices.

BACKGROUND OF THE INVENTION

The spinal column is formed from a number of vertebrae, which in theirnormal state, are separated from each other by cartilaginousintervertebral discs. These discs form a cushion between adjacentvertebrae, resisting compression along the support axis of the spinalcolumn, but permitting limited movement between the vertebrae to providethe characteristic flexible movement of the healthy spine. Injury,disease, or other degenerative disorders may cause one or more of theintervertebral discs to shrink, collapse, deteriorate, or becomedisplaced, herniated, or otherwise damaged.

Intervertebral stabilization by fusion of adjacent vertebrae has provensuccessful in permanently preserving intervertebral spacing. However, anumber of technical barriers exist, including, for example, theretraction of neural elements out of the normal anatomic position, to atemporarily disadvantageous position, to allow reaming, tapping, andinsertion of various intervertebral disc space bone grafts andprostheses. The displacement of neural elements (nerve roots) in suchfashion is not uncommonly followed by temporary, or even permanentinjury to the nerve roots. This can present an unpleasant, nearlyintolerable burning pain in the extremities. Also, traumatic openings inthe nerve covering may occur, allowing the escape of cerebral spinalfluid, and requiring with subsequent repair, resulting scar and nerverestriction. There may also be disruption of motor and sensory nerveelements, potentially causing permanent numbness and weakness in theextremities, bladder, bowel, or genitalia.

Attempts to minimize the disadvantageous effects of retraction of neuralelements include various nerve root retractors, designed to facilitateplacement of the insertion tools against the adjacent nerves, and arecommercially available. One disadvantage of these hand held retractorsis instability. This instability may be caused by movement of theretractors by the insertion tools or by the shifting attention of thesurgical assistant responsible for holding the retractors. Also, thephysical bulk of the retractors themselves requires additional space inthe limited confines of the intervertebral disc space being prepared forthe intervertebral body prosthesis. In view of this, a need exists for aspinal implant insertion instrument to eliminate the need for separatenerve root retractors, and to protect neural elements from injury by thesequence of insertion tools as outlined above.

A need further exists for such a device designed for easy insertion,combining protection and nerve root retraction, at the same timespeeding up the entire operative procedure in a safe and efficientmanner.

Still another need exists for a method of distraction of theintervertebral disc space prior to insertion of the improved spinalimplant. It is to that provision, for a device and method meeting theseand other needs, that the present invention is primarily directed.

BRIEF SUMMARY OF THE INVENTION

The subject invention provides a means for the protection of the nerveroot during the insertion of a spinal implant on bone graft into anintervertebral disc space. Briefly described, in a preferred form, thepresent invention comprises a spinal implant insertion instrument,generally comprising a hollow body with an outer surface and an openinterior surface. A fixed conically shaped curved guide with straightconcave or convex contours extends from the bottom end of the hollowbody. Additionally, a handle element, with a retractable conicallyshaped curved guide, is pivotally attached to the bottom end of thehollow body with an adjustable articulating hinge. The handle element isattached to the hollow body such that the retractable curved guide ispositioned on an opposite side of the hollow body as the fixed curvedguide. The cross-sectional area of the hollow body can be rectangular,elliptical or other shape, so long as it is of sufficient size to allowpassage of instruments for reaming, tapping, and placement ofintervertebral bone grafts or prosthetic devices.

In an alternative form, stringer elements are affixed to the outersurface of the fixed curved guides, where the stringer elements traversethe lengths of the curved guides. The stringer elements add additionalstrength to the curved guides.

In a preferred form, the spinal instrument comprises a primary lockingmechanism. The primary locking mechanism locks the curved guides in thefully extended position by securing the handle element to the hollowbody. Preferably, the locking mechanism is a spring-loaded retractionring, which locks and secures the handle element by engaging a lockingtab, which extends from the handle proximal end.

The spinal implant insertion instrument can be fabricated frombiocompatible materials including, without limitation, titanium,surgical alloys, stainless steel, or any other material suitable forfabrication of surgical instruments.

In a preferred method of, the curved guides are positioned between afirst vertebra and a second vertebra, with the curved guides being inthe un-retracted position. The outer surface of the fixed curved guideis positioned against the lumbar dural tube. The hinged joint allowssimultaneous retraction of the nerve root by compressing the handleelement into the hollow body. The simultaneous retraction of the nerveroot away from the lumbar dural tube allows for a safe retraction of theneural elements, eliminating the need for an independent retractionmeans, which would add additional bulk in a confined space, which in thepresent art, contributes to inappropriate compression of neuralelements. In the retracted position, the internal diameter of the hollowbody is sufficient to allow passage of instruments for reaming, tapping,and placement of intervertebral bone grafts or prosthetic devices.

These and other objects, features and advantages of the presentinvention will be more readily understood, with reference to thedetailed description below, read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a retracted spinal implant insertioninstrument, according to one cylindrical form of the present invention.

FIG. 1a shows an end view of a retracted spinal implant insertioninstrument, according to one cylindrical form of the present invention.

FIG. 2 shows a side view of an un-retracted spinal implant insertioninstrument, according to one cylindrical form of the present invention.

FIG. 3 shows a top view of a retracted spinal implant insertioninstrument, according to one cylindrical form of the present invention.

FIG. 4 shows a cross-sectional side view of a retracted spinal implantinsertion instrument, according to one cylindrical form of the presentinvention.

FIG. 5 shows a side view of the spinal implant insertion instrument insitu according to the cylindrical form of the present invention.

FIG. 6 shows a front view of the un-retracted spinal implant in situaccording to the cylindrical form of the present invention.

FIG. 7 shows a front view of the retracted spinal implant in situaccording to the cylindrical form of the present invention.

FIG. 8 shows a perspective view of the plunger to assist in theretraction of the retractable curved guide.

FIG. 9 shows a perspective view of the hollow guide element.

FIG. 10 shows a cut away side view of the hollow element inserted intothe spinal implant insertion instrument.

FIG. 11 shows a side view of the stringer elements on the fixed andretractable curved guides.

FIG. 12 shows a top view of the stringer elements on the retractablecurved guide.

FIG. 13 shows a side view of a retracted spinal implant insertioninstrument with two retractable curved guides.

FIG. 14 shows a side view of an un-retracted spinal implant insertioninstrument with two retractable curved guides.

FIG. 15 shows a side view of a retracted spinal implant insertioninstrument with a threaded locking means.

FIG. 16 shows a side view of an un-retracted spinal implant insertioninstrument with a threaded locking means.

FIG. 17 shows a side view of a retracted spinal implant insertioninstrument with vertically adjustable articulating hinges.

FIG. 18 shows a side view of a un-retracted spinal implant insertioninstrument with vertically adjustable articulating hinges.

DETAILED DISCLOSURE OF THE INVENTION

Referring now in detail to the figures wherein like reference numbersrepresent like parts throughout, preferred forms of the presentinvention will now be described. As seen in FIGS. 1-3, one embodiment ofthe present invention comprises a spinal implant insertion instrument10, generally comprising a hollow body 12 with an outer surface and anopen interior surface 14. The insertion instrument 10 further comprisesa distal end 17 and a proximal end 15 with a fixed conically shapedcurved guide 16 extending from the distal end 17. Additionally, theinsertion instrument 10 comprises a handle element 18 with a handledistal end 19 and a handle proximal end 21, with a retractable conicallyshaped curved guide 20 extending from the handle distal end 19.

The handle element 18 is pivotally attached to the hollow body 12, suchthat the conically shaped curved guides 16 and 20 are positioned onopposite sides of the hollow body 12. In a preferred embodiment, thehandle distal end 19 is attached to the hollow body 12 distal end 17 byan articulating hinge 22. The articulating hinge 22, allows relativepivotal movement between the hollow body 12 and the handle element 18.

In an alternative embodiment, as shown in FIGS. 17 and 18, thearticulating hinge 22 is vertically adjustable along the length of thehollow body 12 distal end 17. In an embodiment, the hollow body 12distal end 17 comprises a plurality of articulating hinges 22. Thehandle 18 distal end 19 is removable attached to an articulating hinge22 by an attachment pin. The insertion depth of the retractable curveguide 20 may be vertically adjusted by repositioning the handle 18distal end 19 on to the desired articulating hinge 22.

In an alternative embodiment, as shown in FIGS. 11 and 12, stringerelements 44 are affixed to the outer surface of the fixed curved guide16 and to the outer surface of the retractable curved guide 20. Thestringer elements 44 traverse the lengths of the curved guides 16 and20, partially covering the distal end 17 of the hollow body 12 and thedistal end 19 of the handle element 18, respectively. The outer surfaceof each stringer element 44 is sufficiently shaped so as not to causetrauma to the exposed nerves. In a preferred embodiment, the curvedguides 16 and 20 are milled incorporating the stringer elements 44. Inan alternative embodiment, the stringer elements 44 can be affixed tothe curved guides 16 and 20 by welding, or other similar methods knownin the art.

In a further embodiment, as shown in FIGS. 13 and 14, the spinal implantinsertion instrument 10 comprising a hollow body 12 with an outersurface, an open interior surface 14, a distal end 17, and a proximalend 15. The insertion instrument 10 further comprises a handle element18 with a handle distal end 19 and a handle proximal end 21, with aretractable conically shaped curved guide 20 extending from the handledistal end 19. The handle element 18 is pivotally attached to the hollowbody 12 at the distal end 17. The insertion instrument 10 comprises asecond handle element 37, with a handle distal end 62 and a handleproximal end 61, with a second retractable conically shaped curved guide35 extending from the handle distal end 62. The second handle element 37is pivotally attached to the hollow body 12, such that the conicallyshaped curved guides 20 and 35 are positioned on opposite sides of thehollow body 12. In a preferred embodiment, the handle distal ends 19 and62 are attached to the hollow body 12 distal end by articulating hinges22 and 36. The articulating hinges 22 and 36 allow relative pivotalmovement between the hollow body 12 and the handle elements 18 and 37.

The inner diameter of the hollow body 12 is of sufficient size to allowpassage of instruments for vertebral cutting, reaming and tapping, andsubsequent placement of intervertebral bone grafts and prostheticdevices. Preferably, the inner diameter of the hollow body 12 is betweenfrom about 6 millimeters and 24 millimeters.

In an alternative embodiment, the cross-sectional area of the hollowbody 12 can be rectangular, elliptical or other shape, so long as it isof sufficient size to allow passage of instruments for reaming, tapping,and placement of intervertebral bone grafts and prosthetic devices.

In a further embodiment, an impact cap 24 and a primary lockingmechanism 26 are located at the proximal end 15 of the hollow body 12.When engaged, the primary locking mechanism 26 secures the handleelement 18 such that the guides 16 and 20 are in the fully extendedposition. In a preferred embodiment, as shown in FIG. 4, the primarylocking mechanism 26 is a spring-loaded retraction ring 31, which locksand secures the handle element 18 by engaging a locking tab 28, whichextends from the handle proximal end 21.

In an alternative embodiment, as shown in FIGS. 15 and 16, the handleelement 18 is secured to the hollow body 12 by a threadably adjustablelocking mechanism 60. The proximal end 15 of the hollow body 12 and theinterior surface of the primary locking mechanism 26 are match threaded.The primary locking mechanism 26 secures the handle element 18 bythreading the primary locking mechanism 26 onto the locking tab 28. Theprimary locking mechanism 26 releases the handle element 18 by threadingthe primary locking mechanism 26 off of the locking tab 28.

The spinal implant insertion instrument 10 can be fabricated frombiocompatible materials including, without limitation, titanium,surgical alloys, stainless steel, or any other material suitable forfabrication of surgical instruments.

In a preferred method of use, as shown in FIGS. 5-7, the curved guides16 and 20 of the insertion instrument 10 are positioned between a firstvertebra 30 and a second vertebra 32, with the curved guides 16 and 20being in the un-retracted position. As shown in FIG. 6, the spinalimplant 10 is inserted into the intervertebral space, in theun-retracted position, with the outer surface of the fixed curved guide16 being positioned against the lumbar dural tube. The hinged joint 22allows simultaneous retraction of the nerve root by compressing thehandle element 18 into the hollow body 12. The simultaneous retractionof the nerve root away from the lumbar dural tube allows for a saferetraction of the neural elements, eliminating the need for anindependent retraction means, which would add additional bulk in aconfined space, which in the present art, contributes to inappropriatecompression of neural elements. In the retracted position, the internaldiameter of the hollow body 12 is sufficient to allow passage ofinstruments for cutting, reaming and tapping, and subsequent placementof intervertebral bone grafts and prosthetic devices.

In a specific embodiment, a plunger 38, as shown in FIG. 8, can beinserted into the spinal implant insertion instrument 10 to assist inretracting the curved guides 16 and 20. The plunger comprises a shaft 39with a stop 40 located at one end and a wedge 41 located at the oppositeend. Once the curved guides 16 and 20 of the spinal implant insertioninstrument 10 are positioned between a first vertebra 30 and a secondvertebra 32, with the curved guides 16 and 20 being in the un-retractedposition, the wedge 41 is inserted into the proximal end 15 of thehollow body 12. The plunger 38 is pushed through the hollow body 12until the wedge 41 engages the curved guides 16 and 20. The curved guide16 is retracted by simultaneously pushing the wedge 41 through thecurved guides 16 and 20 and compressing the handle element 18 into thehollow body 12. The stop 39 prevents the wedge 41 from being pushedpassed the curved guides 16 and 20. Once the handle element 18 is in thelocked position, the plunger 38 is removed from the hollow body 12. Thecurved guide 16 can be locked in the retracted position to the curvedguide 20 with a minimally larger snap lock flange along it'slongitudinal axis.

In a further embodiment, as shown in FIGS. 9 and 10, a hollow guideelement 46 is inserted into the hollow body 12. The hollow guide element46 has an outer diameter 50 and an inner diameter 48, where the outerdiameter 50 is slightly less than the inner diameter of the hollow body12, such that the hollow guide element 46 can be inserted into thehollow body 12. The inner diameter 48 is of a size sufficient to allowpassage of instruments for reaming, tapping, and subsequent placement ofintervertebral bone grafts and prosthetic devices. A stop 56 ispositioned at the top end 52 of the hollow guide element 46, limitingthe hollow guide element's 46 travel distance. The length of the hollowguide element 46 is substantially equal to the length of the spinalinsertion instrument 10. When the curved guides 16 and 20 are locked inthe fully distracted position the bottom end 54 of the hollow guideelement 46 is inserted into the proximal end 15 of the hollow body 12.In the fully inserted position the bottom end 54 of the hollow guideelement 46 is positioned between the curved guides 16 and 20.

In an alternative embodiment, the cross-sectional area of the hollowguide element can be, for example, rectangular or elliptical in shape,matching the shape of the hollow body 12, and being any of a variety ofsizes, sufficient to allow passage of instruments for reaming, tapping,and placement of intervertebral bone grafts and prosthetic devices.

In another embodiment, the spinal implant insertion instrument 10 can bemore efficiently inserted by first introduction of a distraction tool.The distraction tool comprises a rectangular working surface, presentingfirst, the lesser dimension into the intervertebral disc space, andsecond, rotating the instrument so that the rotational action of thegreater dimension distracts and moves apart the opposing vertebralsurfaces preparatory to placement of the spinal implant insertioninstrument into the center of the intervertebral disc space in it'sretracted form. The spinal insertion instrument 10 can be inserted intothe confined intervertebral disc space without undue retraction ofneural elements, preparatory to placing the spinal implant insertioninstrument into the intervertebral disc space in its retracted form.

Again, when fully deployed in the distracted state, the internaldiameter of the insertion instrument 10 is restored to a sufficientradius to accommodate the previously-mentioned cutting, reaming,tapping, and spinal implant insertion instruments.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only, and various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of thisapplication.

What is claimed is:
 1. A method of inserting a spinal implant or bonegraft comprising the steps of: a) inserting a spinal implant insertioninstrument into the intervertebral space between a first vertebra and asecond vertebra, wherein said spinal insertion instrument comprises ahollow body comprising an outer surface, an inner surface, a proximalend, a distal end, and a first guide, wherein said first guide extendsfrom said distal end of said hollow body, and a handle elementcomprising a handle proximal end, a handle distal end, and a retractableguide, wherein said retractable guide extends from said handle distalend; and said handle distal end is hingedly attached to said distal endof said hollow body, such that said retractable guide opposes said firstguide, wherein said first guide and said retractable guide are inserted,in an un-retracted position, into the intervertebral space between saidfirst and said second vertebrae, wherein an outer surface of said firstguide is positioned against a lumbar dural tube; b) retracting saidspinal implant insertion instrument by compressing said handle elementinto said hollow body, wherein said retractable guide retracts a nerveroot away from the lumbar dural tube; c) locking said retractable guidein the retracted position; d) inserting a spinal implant or bone graftthrough said hollow body into the intervertebral disc space; e)positioning said spinal implant or bone graft in the intervertebralspace; and f) removing said spinal implant insertion instrument from theintervertebral space.
 2. The method of inserting a spinal implant orbone graft according to claim 1, further comprising the steps of: a)inserting cutting, reaming and tapping instruments through said hollowbody into the intervertebral disc; b) cutting, reaming and tapping theintervertebral space; and c) removing said cutting, reaming and tappinginstruments prior to the insertion of the spinal implant or bone graft.3. The method of inserting a spinal implant or bone graft according toclaim 1, further comprising the step of preparing the intervertebralspace by inserting a distractor into the intervertebral space prior toinsertion of a spinal implant insertion instrument.
 4. The method ofinserting a spinal implant or bone graft according to claim 1, furthercomprising the steps of: a) inserting a plunger, comprising a wedgedend, into said hollow body until said wedged end comes into contact withsaid retractable guide; b) retracting said retractable guide bysimultaneously compressing said handle element into said hollow body andpushing said plunger into said hollow body, wherein said retractableguide retracts the nerve root from the lumbar dural tube; c) lockingsaid retractable guide in the retracted position; and d) removing saidplunger from said hollow body prior to the insertion of the spinalimplant or bone graft.
 5. The method of inserting a spinal implant orbone graft according to claim 1, further comprising the step ofinserting a hollow guide element through said hollow body, wherein abottom end of said hollow guide element is positioned between said firstguide and said retractable guide.